INA381: INA381 output offset issue

Alex Yeh

Part Number: INA381
Other Parts Discussed in Thread: LM3643,

Hi team,

We face a problem with using INA381A1 to monitor the current on a LED drive LM3643 output. Once there is no current flow thru the LED bus, there is a output offset voltage around 0.568V at INA381 Vout. Even we short the IN+/IN- together and connect to GND, there is still a 0.55V voltage there. The Vout does not connect to anywhere except the CMPIN. We also tried discount to CMPIN but the offset voltage still exist.

I saw the Vout is able to swing to GND. So it should be not the swing limitation.

Could you provide your comments on what may cause this problem?

Thanks!

Regards,

Alex

over 7 years ago

0 Javier Contreras4 over 7 years ago

TI__Mastermind 35110 points

Alex,

I need to ask some questions. Do you have any resistors at the input. What Rsense are you using? If you can share a schematic that will be useful.

0 Ian Williams over 7 years ago in reply to Javier Contreras4

TI__Mastermind 27715 points

Hello Alex,

It's been several days since your post. Has the issue been resolved? If not, can you please provide the information requested by Javier?

Best regards,

Ian Williams
Applications Manager
Current Sensing

0 Javier Contreras4 over 7 years ago in reply to Ian Williams

TI__Mastermind 35110 points

Moved offline to keep schematic private.

0 Alex Yeh over 7 years ago in reply to Ian Williams

TI__Expert 5805 points

Hi Ian,

I am waiting customer RD checking the things I suggest them to verify. So far they confirm the PCB is is no problem, PCB thermal pad does open for connecting to INA381 GND. But they will try to re-solder the chip. The other thing is that I found no decoupling cap is place at VS+ pin. I am also ask RD to place it and check again.

Regards,

Alex

0 Alex Yeh over 7 years ago in reply to Alex Yeh

TI__Expert 5805 points

Hi Ian and Javier,

I verified this issue is caused by the thermal pad weak soldering. After re-soldering the thermal pad, this issue has resolved. Thanks a lot for great supporting.

Regards,

Alex

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INA381: INA381 output offset issue